Infusion devices and related rescue detection methods

ABSTRACT

Infusion systems, infusion devices, and related operating methods are provided. An exemplary method of operating an infusion device to deliver fluid to a body of a user involves obtaining measurement values for a physiological condition influenced by the fluid, autonomously operating the infusion device to deliver the fluid based at least in part on the measurement values, and detecting a nonactionable condition based on the measurement values. In response to detecting the nonactionable condition, delivery of the fluid is limited while maintaining autonomous operation of the infusion device. In one exemplary embodiment, the nonactionable condition is a rescue condition indicative of the user having consumed fast-acting carbohydrates, and thus insulin delivery may be automatically limited in response to detecting the rescue carbohydrate consumption.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. provisional patentapplication Ser. No. 62/234,471, filed Sep. 29, 2015, the entire contentof which is incorporated by reference herein.

TECHNICAL FIELD

Embodiments of the subject matter described herein relate generally tomedical devices, and more particularly, embodiments of the subjectmatter relate to providing rescue detection and related deliveryprotections during operation of a fluid infusion device.

BACKGROUND

Infusion pump devices and systems are relatively well known in themedical arts, for use in delivering or dispensing an agent, such asinsulin or another prescribed medication, to a patient. A typicalinfusion pump includes a pump drive system which typically includes asmall motor and drive train components that convert rotational motormotion to a translational displacement of a plunger (or stopper) in areservoir that delivers medication from the reservoir to the body of auser via a fluid path created between the reservoir and the body of auser. Use of infusion pump therapy has been increasing, especially fordelivering insulin for diabetics.

Continuous insulin infusion provides greater control of a diabetic'scondition, and hence, control schemes are being developed that allowinsulin infusion pumps to monitor and regulate a user's blood glucoselevel in a substantially continuous and autonomous manner. Regulatingblood glucose level is complicated by variations in the response timefor the type of insulin being used along with variations in a user'sindividual insulin response and daily activities (e.g., exercise,carbohydrate consumption, bolus administration, and the like). Tocompensate for these variations, the amount of insulin being infused inan automated manner may also vary. Reliance solely on currently sensedglucose values may result in delivery adjustments that are too late toavoid a hypoglycemic or hyperglycemic event, so accordingly, predictivealgorithms may be utilized to provide estimations of the future bloodglucose levels as an aid in regulating the blood glucose level.

One scenario that can be problematic occurs when a user consumesfast-acting carbohydrates, for example, to avoid a potentialhypoglycemic event. This, in turn, can result in a spike in the user'sblood glucose level, which, in turn, can result in a rising trend inglucose values indicating a need to deliver insulin to mitigate the risein blood glucose level, thereby unintentionally counteracting thefast-acting carbohydrates. While a quick response time is desired tofacilitate a stable blood glucose level, automatically recovering fromresponding too quickly may not be feasible since infusion devices aregenerally incapable of undoing a previous delivery. Thus, there is aneed to distinguish actionable events that the infusion device shouldrespond to from those that do not require an immediate response.

BRIEF SUMMARY

Infusion systems, infusion devices, and related operating methods areprovided. An embodiment of a method of operating an infusion device todeliver fluid capable of influencing a physiological condition to a bodyof a user is provided. The method involves autonomously operating theinfusion device to deliver the fluid based at least in part onmeasurement values for the physiological condition in the body of theuser, detecting a nonactionable condition, such as a rescue condition,based on one or more of the measurement values, and in response todetecting the nonactionable condition, limiting delivery of the fluidwhile autonomously operating the infusion device.

An embodiment of an infusion system is also provided. The infusionsystem comprises a sensing arrangement to obtain measurement values fora physiological condition from a body of a user and an infusion deviceincluding an actuation arrangement operable to deliver fluid to the bodyof the user and a control system coupled to the actuation arrangement.The fluid influences the physiological condition of the user, and thecontrol system is configured to autonomously operate the actuationarrangement to deliver a variable rate of infusion based on themeasurement values, detect a rescue condition based on one or more ofthe measurement values, and temporarily limit the variable rate ofinfusion in response to the rescue condition.

An apparatus of an infusion device is also provided. The infusion devicecomprises an actuation arrangement operable to deliver fluid to a bodyof a user, a data storage element to maintain control parameters for aclosed-loop operating mode, a communications interface to receivemeasurement values indicative of a physiological condition in the bodyof the user influenced by the fluid, and a control module coupled to theactuation arrangement, the data storage element, and the communicationsinterface. The control module is configured to autonomously operate theactuation arrangement to deliver a variable rate of infusion based onthe measurement values and the control parameters in accordance with theclosed-loop operating mode, detect a rescue condition based on one ormore of the measurement values, and temporarily limit the variable rateof infusion in response to the rescue condition.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the subject matter may be derived byreferring to the detailed description and claims when considered inconjunction with the following figures, wherein like reference numbersrefer to similar elements throughout the figures, which may beillustrated for simplicity and clarity and are not necessarily drawn toscale.

FIG. 1 depicts an exemplary embodiment of an infusion system;

FIG. 2 depicts a plan view of an exemplary embodiment of a fluidinfusion device suitable for use in the infusion system of FIG. 1;

FIG. 3 is an exploded perspective view of the fluid infusion device ofFIG. 2;

FIG. 4 is a cross-sectional view of the fluid infusion device of FIGS.2-3 as viewed along line 4-4 in FIG. 3 when assembled with a reservoirinserted in the infusion device;

FIG. 5 is a block diagram of an exemplary control system suitable foruse in a fluid infusion device, such as the fluid infusion device ofFIG. 1 or FIG. 2;

FIG. 6 is a block diagram of an exemplary pump control system suitablefor use in the control system of FIG. 5;

FIG. 7 is a block diagram of a closed-loop control system that may beimplemented or otherwise supported by the pump control system in thefluid infusion device of FIG. 5 in one or more exemplary embodiments;and

FIG. 8 is a flow diagram of an exemplary rescue management processsuitable for use with the control system of FIG. 5 in one or moreexemplary embodiments.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature andis not intended to limit the embodiments of the subject matter or theapplication and uses of such embodiments. As used herein, the word“exemplary” means “serving as an example, instance, or illustration.”Any implementation described herein as exemplary is not necessarily tobe construed as preferred or advantageous over other implementations.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,brief summary or the following detailed description.

While the subject matter described herein can be implemented in anyelectronic device that includes a motor, exemplary embodiments describedbelow are implemented in the form of medical devices, such as portableelectronic medical devices. Although many different applications arepossible, the following description focuses on a fluid infusion device(or infusion pump) as part of an infusion system deployment. For thesake of brevity, conventional techniques related to infusion systemoperation, insulin pump and/or infusion set operation, and otherfunctional aspects of the systems (and the individual operatingcomponents of the systems) may not be described in detail here. Examplesof infusion pumps may be of the type described in, but not limited to,U.S. Pat. Nos. 4,562,751; 4,685,903; 5,080,653; 5,505,709; 5,097,122;6,485,465; 6,554,798; 6,558,320; 6,558,351; 6,641,533; 6,659,980;6,752,787; 6,817,990; 6,932,584; and 7,621,893; each of which are hereinincorporated by reference.

Embodiments of the subject matter described herein generally relate tofluid infusion devices including a motor that is operable to linearlydisplace a plunger (or stopper) of a reservoir provided within the fluidinfusion device to deliver a dosage of fluid, such as insulin, to thebody of a user. Dosage commands that govern operation of the motor maybe generated in an automated manner in accordance with the deliverycontrol scheme associated with a particular operating mode, and thedosage commands may be generated in a manner that is influenced by acurrent (or most recent) measurement of a physiological condition in thebody of the user. For example, in a closed-loop operating mode, dosagecommands may be generated based on a difference between a current (ormost recent) measurement of the interstitial fluid glucose level in thebody of the user and a target (or reference) glucose value. In thisregard, the rate of infusion may vary as the difference between acurrent measurement value and the target measurement value fluctuates.For purposes of explanation, the subject matter is described herein inthe context of the infused fluid being insulin for regulating a glucoselevel of a user (or patient); however, it should be appreciated thatmany other fluids may be administered through infusion, and the subjectmatter described herein is not necessarily limited to use with insulin.

As described in greater detail below, primarily in the context of FIG.8, in exemplary embodiments described herein, a nonactionable conditionis detected based on the measurement values for a physiologicalcondition in the body of the user while autonomously operating theinfusion device, and in response to detecting the nonactionablecondition, the autonomous delivery of the fluid influencing thephysiological condition is limited, restricted, or otherwise constrainedtemporarily, thereby mitigating any potential response to thenonactionable condition. For purposes of explanation, the subject matteris described herein in the context of the nonactionable condition asbeing a rescue condition where the user has consumed, ingested, orotherwise administered carbohydrates configured to increase his or herblood glucose level and mitigate a potential hypoglycemic event (e.g.,fast-acting or “rescue” carbohydrates). In this regard, the rescuecondition is detected based on a characteristic of the user's glucosemeasurement values, such as, for example, a rate of change in theglucose measurement values over successive samples, which occurs at thesame time as or after the user's glucose measurement values indicate thepotential for a rescue condition exists (e.g., when the user's predictedand/or measured glucose values are low or otherwise indicate a potentialhypoglycemic event exists). In essence, a characteristic signature for arescue condition is detected or otherwise identified from the glucosemeasurement values. Thereafter, the rate of insulin infusion may becapped or otherwise reduced to limit any potential response to therescue condition, so that any consumed rescue carbohydrates can achievetheir intended effect of avoiding a hypoglycemic condition without undueinterference by the autonomous control scheme.

Infusion System Overview

Turning now to FIG. 1, one exemplary embodiment of an infusion system100 includes, without limitation, a fluid infusion device (or infusionpump) 102, a sensing arrangement 104, a command control device (CCD)106, and a computer 108. The components of an infusion system 100 may berealized using different platforms, designs, and configurations, and theembodiment shown in FIG. 1 is not exhaustive or limiting. In practice,the infusion device 102 and the sensing arrangement 104 are secured atdesired locations on the body of a user (or patient), as illustrated inFIG. 1. In this regard, the locations at which the infusion device 102and the sensing arrangement 104 are secured to the body of the user inFIG. 1 are provided only as a representative, non-limiting, example. Theelements of the infusion system 100 may be similar to those described inU.S. Pat. No. 8,674,288, the subject matter of which is herebyincorporated by reference in its entirety.

In the illustrated embodiment of FIG. 1, the infusion device 102 isdesigned as a portable medical device suitable for infusing a fluid, aliquid, a gel, or other agent into the body of a user. In exemplaryembodiments, the infused fluid is insulin, although many other fluidsmay be administered through infusion such as, but not limited to, HIVdrugs, drugs to treat pulmonary hypertension, iron chelation drugs, painmedications, anti-cancer treatments, medications, vitamins, hormones, orthe like. In some embodiments, the fluid may include a nutritionalsupplement, a dye, a tracing medium, a saline medium, a hydrationmedium, or the like.

The sensing arrangement 104 generally represents the components of theinfusion system 100 configured to sense, detect, measure or otherwisequantify a condition of the user, and may include a sensor, a monitor,or the like, for providing data indicative of the condition that issensed, detected, measured or otherwise monitored by the sensingarrangement. In this regard, the sensing arrangement 104 may includeelectronics and enzymes reactive to a biological or physiologicalcondition of the user, such as a blood glucose level, or the like, andprovide data indicative of the blood glucose level to the infusiondevice 102, the CCD 106 and/or the computer 108. For example, theinfusion device 102, the CCD 106 and/or the computer 108 may include adisplay for presenting information or data to the user based on thesensor data received from the sensing arrangement 104, such as, forexample, a current glucose level of the user, a graph or chart of theuser's glucose level versus time, device status indicators, alertmessages, or the like. In other embodiments, the infusion device 102,the CCD 106 and/or the computer 108 may include electronics and softwarethat are configured to analyze sensor data and operate the infusiondevice 102 to deliver fluid to the body of the user based on the sensordata and/or preprogrammed delivery routines. Thus, in exemplaryembodiments, one or more of the infusion device 102, the sensingarrangement 104, the CCD 106, and/or the computer 108 includes atransmitter, a receiver, and/or other transceiver electronics that allowfor communication with other components of the infusion system 100, sothat the sensing arrangement 104 may transmit sensor data or monitordata to one or more of the infusion device 102, the CCD 106 and/or thecomputer 108.

Still referring to FIG. 1, in various embodiments, the sensingarrangement 104 may be secured to the body of the user or embedded inthe body of the user at a location that is remote from the location atwhich the infusion device 102 is secured to the body of the user. Invarious other embodiments, the sensing arrangement 104 may beincorporated within the infusion device 102. In other embodiments, thesensing arrangement 104 may be separate and apart from the infusiondevice 102, and may be, for example, part of the CCD 106. In suchembodiments, the sensing arrangement 104 may be configured to receive abiological sample, analyte, or the like, to measure a condition of theuser.

In various embodiments, the CCD 106 and/or the computer 108 may includeelectronics and other components configured to perform processing,delivery routine storage, and to control the infusion device 102 in amanner that is influenced by sensor data measured by and/or receivedfrom the sensing arrangement 104. By including control functions in theCCD 106 and/or the computer 108, the infusion device 102 may be madewith more simplified electronics. However, in other embodiments, theinfusion device 102 may include all control functions, and may operatewithout the CCD 106 and/or the computer 108. In various embodiments, theCCD 106 may be a portable electronic device. In addition, in variousembodiments, the infusion device 102 and/or the sensing arrangement 104may be configured to transmit data to the CCD 106 and/or the computer108 for display or processing of the data by the CCD 106 and/or thecomputer 108.

In some embodiments, the CCD 106 and/or the computer 108 may provideinformation to the user that facilitates the user's subsequent use ofthe infusion device 102. For example, the CCD 106 may provideinformation to the user to allow the user to determine the rate or doseof medication to be administered into the user's body. In otherembodiments, the CCD 106 may provide information to the infusion device102 to autonomously control the rate or dose of medication administeredinto the body of the user. In some embodiments, the sensing arrangement104 may be integrated into the CCD 106. Such embodiments may allow theuser to monitor a condition by providing, for example, a sample of hisor her blood to the sensing arrangement 104 to assess his or hercondition. In some embodiments, the sensing arrangement 104 and the CCD106 may be used for determining glucose levels in the blood and/or bodyfluids of the user without the use of, or necessity of, a wire or cableconnection between the infusion device 102 and the sensing arrangement104 and/or the CCD 106.

In one or more exemplary embodiments, the sensing arrangement 104 and/orthe infusion device 102 are cooperatively configured to utilize aclosed-loop system for delivering fluid to the user. Examples of sensingdevices and/or infusion pumps utilizing closed-loop systems may be foundat, but are not limited to, the following U.S. Pat. Nos. 6,088,608,6,119,028, 6,589,229, 6,740,072, 6,827,702, 7,323,142, and 7,402,153,all of which are incorporated herein by reference in their entirety. Insuch embodiments, the sensing arrangement 104 is configured to sense ormeasure a condition of the user, such as, blood glucose level or thelike. The infusion device 102 is configured to deliver fluid in responseto the condition sensed by the sensing arrangement 104. In turn, thesensing arrangement 104 continues to sense or otherwise quantify acurrent condition of the user, thereby allowing the infusion device 102to deliver fluid continuously in response to the condition currently (ormost recently) sensed by the sensing arrangement 104 indefinitely. Insome embodiments, the sensing arrangement 104 and/or the infusion device102 may be configured to utilize the closed-loop system only for aportion of the day, for example only when the user is asleep or awake.

FIGS. 2-4 depict one exemplary embodiment of a fluid infusion device 200(or alternatively, infusion pump) suitable for use in an infusionsystem, such as, for example, as infusion device 102 in the infusionsystem 100 of FIG. 1. The fluid infusion device 200 is a portablemedical device designed to be carried or worn by a patient (or user),and the fluid infusion device 200 may leverage any number ofconventional features, components, elements, and characteristics ofexisting fluid infusion devices, such as, for example, some of thefeatures, components, elements, and/or characteristics described in U.S.Pat. Nos. 6,485,465 and 7,621,893. It should be appreciated that FIGS.2-4 depict some aspects of the infusion device 200 in a simplifiedmanner; in practice, the infusion device 200 could include additionalelements, features, or components that are not shown or described indetail herein.

As best illustrated in FIGS. 2-3, the illustrated embodiment of thefluid infusion device 200 includes a housing 202 adapted to receive afluid-containing reservoir 205. An opening 220 in the housing 202accommodates a fitting 223 (or cap) for the reservoir 205, with thefitting 223 being configured to mate or otherwise interface with tubing221 of an infusion set 225 that provides a fluid path to/from the bodyof the user. In this manner, fluid communication from the interior ofthe reservoir 205 to the user is established via the tubing 221. Theillustrated fluid infusion device 200 includes a human-machine interface(HMI) 230 (or user interface) that includes elements 232, 234 that canbe manipulated by the user to administer a bolus of fluid (e.g.,insulin), to change therapy settings, to change user preferences, toselect display features, and the like. The infusion device also includesa display element 226, such as a liquid crystal display (LCD) or anothersuitable display element, that can be used to present various types ofinformation or data to the user, such as, without limitation: thecurrent glucose level of the patient; the time; a graph or chart of thepatient's glucose level versus time; device status indicators; etc.

The housing 202 is formed from a substantially rigid material having ahollow interior 214 adapted to allow an electronics assembly 204, asliding member (or slide) 206, a drive system 208, a sensor assembly210, and a drive system capping member 212 to be disposed therein inaddition to the reservoir 205, with the contents of the housing 202being enclosed by a housing capping member 216. The opening 220, theslide 206, and the drive system 208 are coaxially aligned in an axialdirection (indicated by arrow 218), whereby the drive system 208facilitates linear displacement of the slide 206 in the axial direction218 to dispense fluid from the reservoir 205 (after the reservoir 205has been inserted into opening 220), with the sensor assembly 210 beingconfigured to measure axial forces (e.g., forces aligned with the axialdirection 218) exerted on the sensor assembly 210 responsive tooperating the drive system 208 to displace the slide 206. In variousembodiments, the sensor assembly 210 may be utilized to detect one ormore of the following: an occlusion in a fluid path that slows,prevents, or otherwise degrades fluid delivery from the reservoir 205 toa user's body; when the reservoir 205 is empty; when the slide 206 isproperly seated with the reservoir 205; when a fluid dose has beendelivered; when the infusion pump 200 is subjected to shock orvibration; when the infusion pump 200 requires maintenance.

Depending on the embodiment, the fluid-containing reservoir 205 may berealized as a syringe, a vial, a cartridge, a bag, or the like. Incertain embodiments, the infused fluid is insulin, although many otherfluids may be administered through infusion such as, but not limited to,HIV drugs, drugs to treat pulmonary hypertension, iron chelation drugs,pain medications, anti-cancer treatments, medications, vitamins,hormones, or the like. As best illustrated in FIGS. 3-4, the reservoir205 typically includes a reservoir barrel 219 that contains the fluidand is concentrically and/or coaxially aligned with the slide 206 (e.g.,in the axial direction 218) when the reservoir 205 is inserted into theinfusion pump 200. The end of the reservoir 205 proximate the opening220 may include or otherwise mate with the fitting 223, which securesthe reservoir 205 in the housing 202 and prevents displacement of thereservoir 205 in the axial direction 218 with respect to the housing 202after the reservoir 205 is inserted into the housing 202. As describedabove, the fitting 223 extends from (or through) the opening 220 of thehousing 202 and mates with tubing 221 to establish fluid communicationfrom the interior of the reservoir 205 (e.g., reservoir barrel 219) tothe user via the tubing 221 and infusion set 225. The opposing end ofthe reservoir 205 proximate the slide 206 includes a plunger 217 (orstopper) positioned to push fluid from inside the barrel 219 of thereservoir 205 along a fluid path through tubing 221 to a user. The slide206 is configured to mechanically couple or otherwise engage with theplunger 217, thereby becoming seated with the plunger 217 and/orreservoir 205. Fluid is forced from the reservoir 205 via tubing 221 asthe drive system 208 is operated to displace the slide 206 in the axialdirection 218 toward the opening 220 in the housing 202.

In the illustrated embodiment of FIGS. 3-4, the drive system 208includes a motor assembly 207 and a drive screw 209. The motor assembly207 includes a motor that is coupled to drive train components of thedrive system 208 that are configured to convert rotational motor motionto a translational displacement of the slide 206 in the axial direction218, and thereby engaging and displacing the plunger 217 of thereservoir 205 in the axial direction 218. In some embodiments, the motorassembly 207 may also be powered to translate the slide 206 in theopposing direction (e.g., the direction opposite direction 218) toretract and/or detach from the reservoir 205 to allow the reservoir 205to be replaced. In exemplary embodiments, the motor assembly 207includes a brushless DC (BLDC) motor having one or more permanentmagnets mounted, affixed, or otherwise disposed on its rotor. However,the subject matter described herein is not necessarily limited to usewith BLDC motors, and in alternative embodiments, the motor may berealized as a solenoid motor, an AC motor, a stepper motor, apiezoelectric caterpillar drive, a shape memory actuator drive, anelectrochemical gas cell, a thermally driven gas cell, a bimetallicactuator, or the like. The drive train components may comprise one ormore lead screws, cams, ratchets, jacks, pulleys, pawls, clamps, gears,nuts, slides, bearings, levers, beams, stoppers, plungers, sliders,brackets, guides, bearings, supports, bellows, caps, diaphragms, bags,heaters, or the like. In this regard, although the illustratedembodiment of the infusion pump utilizes a coaxially aligned drivetrain, the motor could be arranged in an offset or otherwise non-coaxialmanner, relative to the longitudinal axis of the reservoir 205.

As best shown in FIG. 4, the drive screw 209 mates with threads 402internal to the slide 206. When the motor assembly 207 is powered andoperated, the drive screw 209 rotates, and the slide 206 is forced totranslate in the axial direction 218. In an exemplary embodiment, theinfusion pump 200 includes a sleeve 211 to prevent the slide 206 fromrotating when the drive screw 209 of the drive system 208 rotates. Thus,rotation of the drive screw 209 causes the slide 206 to extend orretract relative to the drive motor assembly 207. When the fluidinfusion device is assembled and operational, the slide 206 contacts theplunger 217 to engage the reservoir 205 and control delivery of fluidfrom the infusion pump 200. In an exemplary embodiment, the shoulderportion 215 of the slide 206 contacts or otherwise engages the plunger217 to displace the plunger 217 in the axial direction 218. Inalternative embodiments, the slide 206 may include a threaded tip 213capable of being detachably engaged with internal threads 404 on theplunger 217 of the reservoir 205, as described in detail in U.S. Pat.Nos. 6,248,093 and 6,485,465, which are incorporated by referenceherein.

As illustrated in FIG. 3, the electronics assembly 204 includes controlelectronics 224 coupled to the display element 226, with the housing 202including a transparent window portion 228 that is aligned with thedisplay element 226 to allow the display 226 to be viewed by the userwhen the electronics assembly 204 is disposed within the interior 214 ofthe housing 202. The control electronics 224 generally represent thehardware, firmware, processing logic and/or software (or combinationsthereof) configured to control operation of the motor assembly 207and/or drive system 208, as described in greater detail below in thecontext of FIG. 5. Whether such functionality is implemented ashardware, firmware, a state machine, or software depends upon theparticular application and design constraints imposed on the embodiment.Those familiar with the concepts described here may implement suchfunctionality in a suitable manner for each particular application, butsuch implementation decisions should not be interpreted as beingrestrictive or limiting. In an exemplary embodiment, the controlelectronics 224 includes one or more programmable controllers that maybe programmed to control operation of the infusion pump 200.

The motor assembly 207 includes one or more electrical leads 236 adaptedto be electrically coupled to the electronics assembly 204 to establishcommunication between the control electronics 224 and the motor assembly207. In response to command signals from the control electronics 224that operate a motor driver (e.g., a power converter) to regulate theamount of power supplied to the motor from a power supply, the motoractuates the drive train components of the drive system 208 to displacethe slide 206 in the axial direction 218 to force fluid from thereservoir 205 along a fluid path (including tubing 221 and an infusionset), thereby administering doses of the fluid contained in thereservoir 205 into the user's body. Preferably, the power supply isrealized one or more batteries contained within the housing 202.Alternatively, the power supply may be a solar panel, capacitor, AC orDC power supplied through a power cord, or the like. In someembodiments, the control electronics 224 may operate the motor of themotor assembly 207 and/or drive system 208 in a stepwise manner,typically on an intermittent basis; to administer discrete precise dosesof the fluid to the user according to programmed delivery profiles.

Referring to FIGS. 2-4, as described above, the user interface 230includes HMI elements, such as buttons 232 and a directional pad 234,that are formed on a graphic keypad overlay 231 that overlies a keypadassembly 233, which includes features corresponding to the buttons 232,directional pad 234 or other user interface items indicated by thegraphic keypad overlay 231. When assembled, the keypad assembly 233 iscoupled to the control electronics 224, thereby allowing the HMIelements 232, 234 to be manipulated by the user to interact with thecontrol electronics 224 and control operation of the infusion pump 200,for example, to administer a bolus of insulin, to change therapysettings, to change user preferences, to select display features, to setor disable alarms and reminders, and the like. In this regard, thecontrol electronics 224 maintains and/or provides information to thedisplay 226 regarding program parameters, delivery profiles, pumpoperation, alarms, warnings, statuses, or the like, which may beadjusted using the HMI elements 232, 234. In various embodiments, theHMI elements 232, 234 may be realized as physical objects (e.g.,buttons, knobs, joysticks, and the like) or virtual objects (e.g., usingtouch-sensing and/or proximity-sensing technologies). For example, insome embodiments, the display 226 may be realized as a touch screen ortouch-sensitive display, and in such embodiments, the features and/orfunctionality of the HMI elements 232, 234 may be integrated into thedisplay 226 and the HMI 230 may not be present. In some embodiments, theelectronics assembly 204 may also include alert generating elementscoupled to the control electronics 224 and suitably configured togenerate one or more types of feedback, such as, without limitation:audible feedback; visual feedback; haptic (physical) feedback; or thelike.

Referring to FIGS. 3-4, in accordance with one or more embodiments, thesensor assembly 210 includes a back plate structure 250 and a loadingelement 260. The loading element 260 is disposed between the cappingmember 212 and a beam structure 270 that includes one or more beamshaving sensing elements disposed thereon that are influenced bycompressive force applied to the sensor assembly 210 that deflects theone or more beams, as described in greater detail in U.S. Pat. No.8,474,332, which is incorporated by reference herein. In exemplaryembodiments, the back plate structure 250 is affixed, adhered, mounted,or otherwise mechanically coupled to the bottom surface 238 of the drivesystem 208 such that the back plate structure 250 resides between thebottom surface 238 of the drive system 208 and the housing cap 216. Thedrive system capping member 212 is contoured to accommodate and conformto the bottom of the sensor assembly 210 and the drive system 208. Thedrive system capping member 212 may be affixed to the interior of thehousing 202 to prevent displacement of the sensor assembly 210 in thedirection opposite the direction of force provided by the drive system208 (e.g., the direction opposite direction 218). Thus, the sensorassembly 210 is positioned between the motor assembly 207 and secured bythe capping member 212, which prevents displacement of the sensorassembly 210 in a downward direction opposite the direction of arrow218, such that the sensor assembly 210 is subjected to a reactionarycompressive force when the drive system 208 and/or motor assembly 207 isoperated to displace the slide 206 in the axial direction 218 inopposition to the fluid pressure in the reservoir 205. Under normaloperating conditions, the compressive force applied to the sensorassembly 210 is correlated with the fluid pressure in the reservoir 205.As shown, electrical leads 240 are adapted to electrically couple thesensing elements of the sensor assembly 210 to the electronics assembly204 to establish communication to the control electronics 224, whereinthe control electronics 224 are configured to measure, receive, orotherwise obtain electrical signals from the sensing elements of thesensor assembly 210 that are indicative of the force applied by thedrive system 208 in the axial direction 218.

FIG. 5 depicts an exemplary embodiment of a control system 500 suitablefor use with an infusion device 502, such as the infusion device 102 inFIG. 1 or the infusion device 200 of FIG. 2. The control system 500 iscapable of controlling or otherwise regulating a physiological conditionin the body 501 of a user to a desired (or target) value or otherwisemaintain the condition within a range of acceptable values in anautomated or autonomous manner. In one or more exemplary embodiments,the condition being regulated is sensed, detected, measured or otherwisequantified by a sensing arrangement 504 (e.g., sensing arrangement 104)communicatively coupled to the infusion device 502. However, it shouldbe noted that in alternative embodiments, the condition being regulatedby the control system 500 may be correlative to the measured valuesobtained by the sensing arrangement 504. That said, for clarity andpurposes of explanation, the subject matter may be described herein inthe context of the sensing arrangement 504 being realized as a glucosesensing arrangement that senses, detects, measures or otherwisequantifies the user's glucose level, which is being regulated in thebody 501 of the user by the control system 500.

In exemplary embodiments, the sensing arrangement 504 includes one ormore interstitial glucose sensing elements that generate or otherwiseoutput electrical signals having a signal characteristic that iscorrelative to, influenced by, or otherwise indicative of the relativeinterstitial fluid glucose level in the body 501 of the user. The outputelectrical signals are filtered or otherwise processed to obtain ameasurement value indicative of the user's interstitial fluid glucoselevel. In exemplary embodiments, a blood glucose meter 530, such as afinger stick device, is utilized to directly sense, detect, measure orotherwise quantify the blood glucose in the body 501 of the user. Inthis regard, the blood glucose meter 530 outputs or otherwise provides ameasured blood glucose value that may be utilized as a referencemeasurement for calibrating the sensing arrangement 504 and converting ameasurement value indicative of the user's interstitial fluid glucoselevel into a corresponding calibrated blood glucose value. For purposesof explanation, the calibrated blood glucose value calculated based onthe electrical signals output by the sensing element(s) of the sensingarrangement 504 may alternatively be referred to herein as the sensorglucose value, the sensed glucose value, or variants thereof.

In the illustrated embodiment, the pump control system 520 generallyrepresents the electronics and other components of the infusion device502 that control operation of the fluid infusion device 502 according toa desired infusion delivery program in a manner that is influenced bythe sensed glucose value indicative of a current glucose level in thebody 501 of the user. For example, to support a closed-loop operatingmode, the pump control system 520 maintains, receives, or otherwiseobtains a target or commanded glucose value, and automatically generatesor otherwise determines dosage commands for operating an actuationarrangement, such as a motor 507, to displace the plunger 517 anddeliver insulin to the body 501 of the user based on the differencebetween a sensed glucose value and the target glucose value. In otheroperating modes, the pump control system 520 may generate or otherwisedetermine dosage commands configured to maintain the sensed glucosevalue below an upper glucose limit, above a lower glucose limit, orotherwise within a desired range of glucose values. In practice, theinfusion device 502 may store or otherwise maintain the target value,upper and/or lower glucose limit(s), and/or other glucose thresholdvalue(s) in a data storage element accessible to the pump control system520.

The target glucose value and other threshold glucose values may bereceived from an external component (e.g., CCD 106 and/or computingdevice 108) or be input by a user via a user interface element 540associated with the infusion device 502. In practice, the one or moreuser interface element(s) 540 associated with the infusion device 502typically include at least one input user interface element, such as,for example, a button, a keypad, a keyboard, a knob, a joystick, amouse, a touch panel, a touchscreen, a microphone or another audio inputdevice, and/or the like. Additionally, the one or more user interfaceelement(s) 540 include at least one output user interface element, suchas, for example, a display element (e.g., a light-emitting diode or thelike), a display device (e.g., a liquid crystal display or the like), aspeaker or another audio output device, a haptic feedback device, or thelike, for providing notifications or other information to the user. Itshould be noted that although FIG. 5 depicts the user interfaceelement(s) 540 as being separate from the infusion device 502, inpractice, one or more of the user interface element(s) 540 may beintegrated with the infusion device 502. Furthermore, in someembodiments, one or more user interface element(s) 540 are integratedwith the sensing arrangement 504 in addition to and/or in alternative tothe user interface element(s) 540 integrated with the infusion device502. The user interface element(s) 540 may be manipulated by the user tooperate the infusion device 502 to deliver correction boluses, adjusttarget and/or threshold values, modify the delivery control scheme oroperating mode, and the like, as desired.

Still referring to FIG. 5, in the illustrated embodiment, the infusiondevice 502 includes a motor control module 512 coupled to a motor 507(e.g., motor assembly 207) that is operable to displace a plunger 517(e.g., plunger 217) in a reservoir (e.g., reservoir 205) and provide adesired amount of fluid to the body 501 of a user. In this regard,displacement of the plunger 517 results in the delivery of a fluid thatis capable of influencing the condition in the body 501 of the user tothe body 501 of the user via a fluid delivery path (e.g., via tubing 221of an infusion set 225). A motor driver module 514 is coupled between anenergy source 503 and the motor 507. The motor control module 512 iscoupled to the motor driver module 514, and the motor control module 512generates or otherwise provides command signals that operate the motordriver module 514 to provide current (or power) from the energy source503 to the motor 507 to displace the plunger 517 in response toreceiving, from a pump control system 520, a dosage command indicativeof the desired amount of fluid to be delivered.

In exemplary embodiments, the energy source 503 is realized as a batteryhoused within the infusion device 502 (e.g., within housing 202) thatprovides direct current (DC) power. In this regard, the motor drivermodule 514 generally represents the combination of circuitry, hardwareand/or other electrical components configured to convert or otherwisetransfer DC power provided by the energy source 503 into alternatingelectrical signals applied to respective phases of the stator windingsof the motor 507 that result in current flowing through the statorwindings that generates a stator magnetic field and causes the rotor ofthe motor 507 to rotate. The motor control module 512 is configured toreceive or otherwise obtain a commanded dosage from the pump controlsystem 520, convert the commanded dosage to a commanded translationaldisplacement of the plunger 517, and command, signal, or otherwiseoperate the motor driver module 514 to cause the rotor of the motor 507to rotate by an amount that produces the commanded translationaldisplacement of the plunger 517. For example, the motor control module512 may determine an amount of rotation of the rotor required to producetranslational displacement of the plunger 517 that achieves thecommanded dosage received from the pump control system 520. Based on thecurrent rotational position (or orientation) of the rotor with respectto the stator that is indicated by the output of the rotor sensingarrangement 516, the motor control module 512 determines the appropriatesequence of alternating electrical signals to be applied to therespective phases of the stator windings that should rotate the rotor bythe determined amount of rotation from its current position (ororientation). In embodiments where the motor 507 is realized as a BLDCmotor, the alternating electrical signals commutate the respectivephases of the stator windings at the appropriate orientation of therotor magnetic poles with respect to the stator and in the appropriateorder to provide a rotating stator magnetic field that rotates the rotorin the desired direction. Thereafter, the motor control module 512operates the motor driver module 514 to apply the determined alternatingelectrical signals (e.g., the command signals) to the stator windings ofthe motor 507 to achieve the desired delivery of fluid to the user.

When the motor control module 512 is operating the motor driver module514, current flows from the energy source 503 through the statorwindings of the motor 507 to produce a stator magnetic field thatinteracts with the rotor magnetic field. In some embodiments, after themotor control module 512 operates the motor driver module 514 and/ormotor 507 to achieve the commanded dosage, the motor control module 512ceases operating the motor driver module 514 and/or motor 507 until asubsequent dosage command is received. In this regard, the motor drivermodule 514 and the motor 507 enter an idle state during which the motordriver module 514 effectively disconnects or isolates the statorwindings of the motor 507 from the energy source 503. In other words,current does not flow from the energy source 503 through the statorwindings of the motor 507 when the motor 507 is idle, and thus, themotor 507 does not consume power from the energy source 503 in the idlestate, thereby improving efficiency.

Depending on the embodiment, the motor control module 512 may beimplemented or realized with a general purpose processor, amicroprocessor, a controller, a microcontroller, a state machine, acontent addressable memory, an application specific integrated circuit,a field programmable gate array, any suitable programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof, designed to perform the functions described herein.In exemplary embodiments, the motor control module 512 includes orotherwise accesses a data storage element or memory, including any sortof random access memory (RAM), read only memory (ROM), flash memory,registers, hard disks, removable disks, magnetic or optical massstorage, or any other short or long term storage media or othernon-transitory computer-readable medium, which is capable of storingprogramming instructions for execution by the motor control module 512.The computer-executable programming instructions, when read and executedby the motor control module 512, cause the motor control module 512 toperform or otherwise support the tasks, operations, functions, andprocesses described herein.

It should be appreciated that FIG. 5 is a simplified representation ofthe infusion device 502 for purposes of explanation and is not intendedto limit the subject matter described herein in any way. In this regard,depending on the embodiment, some features and/or functionality of thesensing arrangement 504 may implemented by or otherwise integrated intothe pump control system 520, or vice versa. Similarly, in practice, thefeatures and/or functionality of the motor control module 512 mayimplemented by or otherwise integrated into the pump control system 520,or vice versa. Furthermore, the features and/or functionality of thepump control system 520 may be implemented by control electronics 224located in the fluid infusion device 200, 400, while in alternativeembodiments, the pump control system 520 may be implemented by a remotecomputing device that is physically distinct and/or separate from theinfusion device 502, such as, for example, the CCD 106 or the computingdevice 108.

FIG. 6 depicts an exemplary embodiment of a pump control system 600suitable for use as the pump control system 520 in FIG. 5 in accordancewith one or more embodiments. The illustrated pump control system 600includes, without limitation, a pump control module 602, acommunications interface 604, and a data storage element (or memory)606. The pump control module 602 is coupled to the communicationsinterface 604 and the memory 606, and the pump control module 602 issuitably configured to support the operations, tasks, and/or processesdescribed herein. In exemplary embodiments, the pump control module 602is also coupled to one or more user interface elements 608 (e.g., userinterface 230, 540) for receiving user input and providingnotifications, alerts, or other therapy information to the user.Although FIG. 6 depicts the user interface element 608 as being separatefrom the pump control system 600, in various alternative embodiments,the user interface element 608 may be integrated with the pump controlsystem 600 (e.g., as part of the infusion device 200, 502), the sensingarrangement 504 or another element of an infusion system 100 (e.g., thecomputer 108 or CCD 106).

Referring to FIG. 6 and with reference to FIG. 5, the communicationsinterface 604 generally represents the hardware, circuitry, logic,firmware and/or other components of the pump control system 600 that arecoupled to the pump control module 602 and configured to supportcommunications between the pump control system 600 and the sensingarrangement 504. In this regard, the communications interface 604 mayinclude or otherwise be coupled to one or more transceiver modulescapable of supporting wireless communications between the pump controlsystem 520, 600 and the sensing arrangement 504 or another electronicdevice 106, 108 in an infusion system 100. In other embodiments, thecommunications interface 604 may be configured to support wiredcommunications to/from the sensing arrangement 504.

The pump control module 602 generally represents the hardware,circuitry, logic, firmware and/or other component of the pump controlsystem 600 that is coupled to the communications interface 604 andconfigured to determine dosage commands for operating the motor 506 todeliver fluid to the body 501 based on data received from the sensingarrangement 504 and perform various additional tasks, operations,functions and/or operations described herein. For example, in exemplaryembodiments, pump control module 602 implements or otherwise executes acommand generation application 610 that supports one or more autonomousoperating modes and calculates or otherwise determines dosage commandsfor operating the motor 506 of the infusion device 502 in an autonomousoperating mode based at least in part on a current measurement value fora condition in the body 501 of the user. For example, in a closed-loopoperating mode, the command generation application 610 may determine adosage command for operating the motor 506 to deliver insulin to thebody 501 of the user based at least in part on the current glucosemeasurement value most recently received from the sensing arrangement504 to regulate the user's blood glucose level to a target referenceglucose value. Additionally, the command generation application 610 maygenerate dosage commands for boluses that are manually-initiated orotherwise instructed by a user via a user interface element 608. Forexample, regardless of the operating mode being implemented, the commandgeneration application 610 may determine a dosage command for operatingthe motor 506 to deliver a bolus of insulin to the body 501 of the userthat corresponds to a correction bolus or meal bolus amount selected orotherwise indicated by the user via the user interface element 230, 540,608.

Still referring to FIG. 6, depending on the embodiment, the pump controlmodule 602 may be implemented or realized with a general purposeprocessor, a microprocessor, a controller, a microcontroller, a statemachine, a content addressable memory, an application specificintegrated circuit, a field programmable gate array, any suitableprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof, designed to perform thefunctions described herein. In this regard, the steps of a method oralgorithm described in connection with the embodiments disclosed hereinmay be embodied directly in hardware, in firmware, in a software moduleexecuted by the pump control module 602, or in any practical combinationthereof. In exemplary embodiments, the pump control module 602 includesor otherwise accesses the data storage element or memory 606, which maybe realized using any sort of non-transitory computer-readable mediumcapable of storing programming instructions for execution by the pumpcontrol module 602. The computer-executable programming instructions,when read and executed by the pump control module 602, cause the pumpcontrol module 602 to implement or otherwise generate the commandgeneration application 610 and perform the tasks, operations, functions,and processes described in greater detail below.

It should be understood that FIG. 6 is a simplified representation of apump control system 600 for purposes of explanation and is not intendedto limit the subject matter described herein in any way. For example, insome embodiments, the features and/or functionality of the motor controlmodule 512 may be implemented by or otherwise integrated into the pumpcontrol system 600 and/or the pump control module 602, for example, bythe command generation application 610 converting the dosage commandinto a corresponding motor command, in which case, the separate motorcontrol module 512 may be absent from an embodiment of the infusiondevice 502.

FIG. 7 depicts an exemplary closed-loop control system 700 that may beimplemented by a pump control system 520, 600 to provide a closed-loopoperating mode that autonomously regulates a condition in the body of auser to a reference (or target) value. It should be appreciated thatFIG. 7 is a simplified representation of the control system 700 forpurposes of explanation and is not intended to limit the subject matterdescribed herein in any way.

In exemplary embodiments, the control system 700 receives or otherwiseobtains a target glucose value at input 702. In some embodiments, thetarget glucose value may be stored or otherwise maintained by theinfusion device 502 (e.g., in memory 606), however, in some alternativeembodiments, the target value may be received from an external component(e.g., CCD 106 and/or computer 108). In one or more embodiments, thetarget glucose value may be dynamically calculated or otherwisedetermined prior to entering the closed-loop operating mode based on oneor more patient-specific control parameters. For example, the targetblood glucose value may be calculated based at least in part on apatient-specific reference basal rate and a patient-specific dailyinsulin requirement, which are determined based on historical deliveryinformation over a preceding interval of time (e.g., the amount ofinsulin delivered over the preceding 24 hours). The control system 700also receives or otherwise obtains a current glucose measurement value(e.g., the most recently obtained sensor glucose value) from the sensingarrangement 504 at input 704. The illustrated control system 700implements or otherwise provides proportional-integral-derivative (PID)control to determine or otherwise generate delivery commands foroperating the motor 510 based at least in part on the difference betweenthe target glucose value and the current glucose measurement value. Inthis regard, the PID control attempts to minimize the difference betweenthe measured value and the target value, and thereby regulates themeasured value to the desired value. PID control parameters are appliedto the difference between the target glucose level at input 702 and themeasured glucose level at input 704 to generate or otherwise determine adosage (or delivery) command provided at output 730. Based on thatdelivery command, the motor control module 512 operates the motor 510 todeliver insulin to the body of the user to influence the user's glucoselevel, and thereby reduce the difference between a subsequently measuredglucose level and the target glucose level.

The illustrated control system 700 includes or otherwise implements asummation block 706 configured to determine a difference between thetarget value obtained at input 702 and the measured value obtained fromthe sensing arrangement 504 at input 704, for example, by subtractingthe target value from the measured value. The output of the summationblock 706 represents the difference between the measured and targetvalues, which is then provided to each of a proportional term path, anintegral term path, and a derivative term path. The proportional termpath includes a gain block 720 that multiplies the difference by aproportional gain coefficient, K_(P), to obtain the proportional term.The integral term path includes an integration block 708 that integratesthe difference and a gain block 722 that multiplies the integrateddifference by an integral gain coefficient, K_(I), to obtain theintegral term. The derivative term path includes a derivative block 710that determines the derivative of the difference and a gain block 724that multiplies the derivative of the difference by a derivative gaincoefficient, K_(D), to obtain the derivative term. The proportionalterm, the integral term, and the derivative term are then added orotherwise combined to obtain a delivery command that is utilized tooperate the motor at output 730. Various implementation detailspertaining to closed-loop PID control and determine gain coefficientsare described in greater detail in U.S. Pat. No. 7,402,153, which isincorporated by reference.

In one or more exemplary embodiments, the PID gain coefficients areuser-specific (or patient-specific) and dynamically calculated orotherwise determined prior to entering the closed-loop operating modebased on historical insulin delivery information (e.g., amounts and/ortimings of previous dosages, historical correction bolus information, orthe like), historical sensor measurement values, historical referenceblood glucose measurement values, user-reported or user-input events(e.g., meals, exercise, and the like), and the like. In this regard, oneor more patient-specific control parameters (e.g., an insulinsensitivity factor, a daily insulin requirement, an insulin limit, areference basal rate, a reference fasting glucose, an active insulinaction duration, pharmodynamical time constants, or the like) may beutilized to compensate, correct, or otherwise adjust the PID gaincoefficients to account for various operating conditions experiencedand/or exhibited by the infusion device 502. The PID gain coefficientsmay be maintained by the memory 606 accessible to the pump controlmodule 602. In this regard, the memory 606 may include a plurality ofregisters associated with the control parameters for the PID control.For example, a first parameter register may store the target glucosevalue and be accessed by or otherwise coupled to the summation block 706at input 702, and similarly, a second parameter register accessed by theproportional gain block 720 may store the proportional gain coefficient,a third parameter register accessed by the integration gain block 722may store the integration gain coefficient, and a fourth parameterregister accessed by the derivative gain block 724 may store thederivative gain coefficient.

Rescue Detection

In exemplary embodiments described herein, a pump control system 520,600 is configured to detect a rescue condition which should benonactionable in terms of insulin delivery based on the glucosemeasurement values obtained from the sensing arrangement 504 whileautonomously operating the infusion device 502, and in response,automatically caps, limits, or otherwise restricts insulin deliverytemporarily, thereby limiting the response or action that wouldotherwise be taken by the infusion device 502 autonomously in responseto the rescue condition. Thus, when a user consumes fast-acting (or“rescue”) carbohydrates to avoid a potential hypoglycemic event whilethe infusion device is in a closed-loop operating mode, the pump controlsystem 520, 600 recognizes a change in one or more characteristic(s) ofthe glucose measurement values indicative of a rescue condition andadjusts the autonomous operation of the infusion device in a manner thattemporarily reduces insulin delivery. In this regard, once the rescuecondition has expired or otherwise elapsed, the pump control system 520,600 restores the delivery of insulin to the preceding delivery settings.Thus, the pump control system 520, 600 essentially treats a detectedrescue condition a nonactionable event and alters the autonomousoperation to allow the carbohydrates consumed by the user to achievetheir intended effect before resuming normal or preceding regulation ofthe user's glucose level.

FIG. 8 depicts an exemplary rescue management process 800 suitable forimplementation by a control system associated with a fluid infusiondevice, such as a control system 500, 520, 600 in the infusion device502, to automatically adjust the fluid delivery in a manner thataccounts for events that should essentially be nonactionable, such as arescue condition attributable to a user consuming rescue carbohydrates.For purposes of explanation, the subject matter is described herein inthe context of detecting a rescue condition during implementation of aclosed-loop operating mode to regulate a user's glucose level; however,it should be appreciated that the subject matter described herein is notnecessarily limited to any particular initial operating mode or anyparticular type of condition being detected.

The various tasks performed in connection with the rescue managementprocess 800 may be performed by hardware, firmware, software executed byprocessing circuitry, or any combination thereof. For illustrativepurposes, the following description refers to elements mentioned abovein connection with FIGS. 1-7. In practice, portions of the rescuemanagement process 800 may be performed by different elements of thecontrol system 500, such as, for example, the infusion device 502, thesensing arrangement 504, the pump control system 520, 600, the pumpcontrol module 602, and/or the command generation application 610. Itshould be appreciated that the rescue management process 800 may includeany number of additional or alternative tasks, the tasks need not beperformed in the illustrated order and/or the tasks may be performedconcurrently, and/or the rescue management process 800 may beincorporated into a more comprehensive procedure or process havingadditional functionality not described in detail herein. Moreover, oneor more of the tasks shown and described in the context of FIG. 8 couldbe omitted from a practical embodiment of the rescue management process800 as long as the intended overall functionality remains intact.

Referring to FIG. 8 with continued reference to FIGS. 1-7, in exemplaryembodiments, the rescue management process 800 is performed while aninfusion device is being operated in an autonomous operating mode, suchas a closed-loop operating mode. The rescue management processinitializes or otherwise begins by obtaining the current (or mostrecent) glucose measurement from the sensing arrangement and determineswhether the current glucose measurement is less than a rescue monitoringthreshold (tasks 802, 804). The control system 520, 600 compares thecurrent sensor glucose measurement value from the sensing arrangement504 (e.g., the value input to the closed-loop control system 700 atinput 704) to a monitoring threshold value and detects or otherwiseidentifies when the current glucose measurement value is less than themonitoring threshold value. In this regard, the rescue monitoringthreshold value corresponds to a glucose level below which a user islikely to consume rescue carbohydrates so that the rescue managementprocess 800 does not limit insulin delivery at higher glucose levelswhere it is unlikely that the user will consume rescue carbohydrates.For example, in one or more embodiments, a threshold value for alertingthe user to a potential hypoglycemic event may also be utilized as therescue monitoring threshold value, or alternatively, the rescuemonitoring threshold value may be equal to an alerting threshold valueplus an offset value (e.g., to account for a user manually identifying apotential hypoglycemic condition and consuming rescue carbohydrates inadvance of an alert). In embodiments where the pump control system 520,600 is configured to alert a user to consume rescue carbohydrates, therescue monitoring threshold value may be equal to the threshold valueused to generate the rescue carbohydrate alert.

When the rescue management process 800 identifies the current glucosemeasurement is greater than the rescue monitoring threshold, theautonomous operation of the infusion device is maintained in its currentstate. For example, in a closed-loop operating mode, the pump controlsystem 520, 600 may autonomously operate the motor 507 of the infusiondevice 502 to deliver a variable rate of insulin infusion based at leastin part on the difference between the current sensor glucose measurementvalue and a target glucose value configured to regulate the sensorglucose measurement values to the target glucose value, as describedabove in the context of FIG. 7.

When the rescue management process 800 identifies the current glucosemeasurement is less than the rescue monitoring threshold, the rescuemanagement process 800 verifies or otherwise confirms that there has notbeen a meal announcement (task 806). In this regard, when a usermanipulates the user interface 540, 608 to initiate a meal bolus orotherwise indicate that a meal is about to be consumed, the rescuemanagement process 800 exits or otherwise terminates, thereby allowingthe meal bolus to be delivered unimpeded and with the autonomousoperating mode maintaining its current manner of glucose regulation.

In the absence of a meal announcement, the rescue management process 800monitors or otherwise analyzes subsequent glucose measurements for oneor more characteristics indicative of the user having consumed rescuecarbohydrates and detects a rescue condition with the characteristic(s)violate a rescue threshold (tasks 808, 810). In exemplary embodiments,for each new glucose measurement value received during a monitoringwindow after detecting a glucose measurement below the monitoringthreshold, the pump control system 520, 600 calculates or otherwisedetermines a rate of change associated with the respective glucosemeasurement value and detects a rescue condition when the rate of changeassociated with the current (or most recent) glucose measurement valueexceeds a rescue threshold. For example, the pump control system 520,600 may calculate the rate of change as the difference between thecurrent sensor glucose measurement and the preceding sensor glucosemeasurement, where the rescue threshold value represents a change inglucose measurement values over successive samplings indicative of theuser having consumed fast-acting rescue carbohydrates. In someembodiments, one or more of the current sensor glucose measurement, thepreceding sensor glucose measurement and/or the rate of changeassociated with the current sensor glucose measurement may be determinedby filtering a plurality of preceding glucose measurements. For example,the current sensor glucose measurement most recently received from asensing arrangement 504 may be updated every 5 minutes, where eachcurrent sensor glucose measurement is a filtered average of fivepreceding output signals sampled at one minute intervals from thesensing element sensitive to a user's glucose level, resulting in afiltered measurement indicative of the user's current glucose level.Some examples of such filtering are described in U.S. patent applicationSer. No. 14/281,766, which is incorporated by reference herein in itsentirety.

In the absence of glucose measurements indicative of a rescue condition,the rescue management process 800 verifies or otherwise determineswhether the rescue monitoring window has elapsed or expired (task 812).In this regard, the pump control system 520, 600 initiates a timer upondetecting a glucose measurement less than a rescue monitoring thresholdand ceases monitoring for a rescue condition once the timer valueexceeds a value corresponding to a monitoring window duration. Therescue monitoring window duration corresponds to an average duration ortime period after consumption during which fast-acting rescuecarbohydrates are likely to exhibit an effect on the user's sensorglucose measurement values. For example, the rescue monitoring windowduration may be chosen to be 25 minutes or less. In this regard, whenthe rate of change between any two successive measurement values doesnot violate the rescue condition detection threshold within the rescuemonitoring window, it may be presumed that any carbohydrates consumedwere not fast-acting and therefore should be responded to in a normalmanner as dictated by the current control scheme or operating mode ineffect.

In the illustrated embodiment, the rescue management process 800terminates or exits when the monitoring window has elapsed, therebymaintaining the normal autonomous operation of the infusion device.However, in other embodiments, the rescue management process 800 mayrepeat the task of determining whether the current glucose measurementis less than the rescue monitoring threshold after expiration of themonitoring window (task 804), and if so, the rescue management process800 repeats the loop defined by tasks 806, 808, 810, 812 to detect orotherwise identify a potential rescue condition for as long as theglucose measurements are less than the rescue monitoring threshold uponexpiration of a monitoring window. Thus, the rescue management process800 may continue to monitor for a rescue condition for as long as thecurrent glucose measurement is less than the rescue monitoring thresholduntil the user's glucose measurements rise above the rescue monitoringthreshold to a more normal level.

In response to detecting a rescue condition, the rescue managementprocess 800 automatically modifies or otherwise adjusts one or moredelivery settings utilized for autonomously operating the infusiondevice to limit or otherwise restrict the delivery of fluid for atemporary period of time (tasks 814, 816). For example, in oneembodiment, the pump control system 520, 600 modifies or otherwiseadjusts the maximum delivery rate or maximum dosage associated with theautonomous operating mode from an initial value to a lower value totemporarily cap the dosage commands generated based on the user'sglucose measurement values. In this regard, as a difference between theuser's current or predicted glucose measurement value increases inresponse to the user metabolizing the rescue carbohydrates, the dosagecommand generated by the pump control system 520, 600 based on thatdifference in a closed-loop operating mode may be reduced or otherwiseconstrained to the maximum dosage, regardless of the magnitude of thedifference. For example, the maximum delivery rate for the closed-loopoperating mode may be temporarily set to a patient-specific safe basalrate of infusion, which may be a fraction of the normal maximum deliveryrate for the closed-loop operating mode. In this manner, the responsetime for the closed-loop control is increased, thereby reducing theautonomous response or action taken in response to the rescuecarbohydrates. In another embodiment, the pump control system 520, 600modifies or otherwise adjusts values for one or more control parameters(e.g., one or more PID gain coefficients 720, 722, 724) to decrease theresponsiveness of the autonomous control scheme and thereby limit thedosage or delivery rate that would otherwise be implemented in responseto the rise in the user's glucose level.

In one or more embodiments, the pump control system 520, 600automatically transitions from a closed-loop operating mode to a rescuemode having an associated maximum delivery rate (or maximum dosage) thatis less than the maximum delivery rate associated with the closed-loopoperating mode. In the rescue mode, the pump control system 520, 600 maycontinue to generate dosage commands in a manner that is influenced bythe current glucose measurement value (or a predicted glucosemeasurement value based thereon) in a similar manner as is done in theclosed-loop operating mode, albeit with the dosage commands being cappedor limited to a lower maximum value. In other embodiments, the pumpcontrol system 520, 600 may generate dosage commands in a manner similarto the closed-loop operating mode, but with the dosage commands beingproportionally scaled down, for example, based on the ratio of thelimited maximum delivery rate to the normal closed-loop maximum deliveryrate. In yet other embodiments, the rescue mode may correspond to apreexisting safe mode supported by the infusion device 502, in whichcase the pump control system 520, 600 automatically transitions from aclosed-loop operating mode to the safe mode in response to the rescuecondition. The safe mode is characterized by a reduced or limited rateof delivery of insulin relative to the normal closed-loop operatingmode, for example, by having a lower maximum delivery rate, controlparameters coefficients adjusted for a slower response time, or thelike.

Still referring to FIG. 8, while autonomously operating the infusiondevice in a manner that limits delivery, the rescue management process800 monitors for an exit condition, and in response to detecting an exitcondition, the rescue management process 800 automatically restores theinfusion delivery to the initial configuration or settings prior todetecting the rescue condition (tasks 816, 818). For example, in one ormore embodiments, the pump control system 520, 600 may continuallymonitor or otherwise analyze glucose and/or predicted glucosemeasurement values received from the sensing arrangement 504 to detector otherwise identify an absence of a rescue condition. In this regard,the pump control system 520, 600 may detect characteristics of theglucose measurement values indicative of the rescue carbohydrates beingmetabolized by the user, such as, for example, when a rate of changebetween several successive glucose measurement values is less than orequal to zero. In other embodiments, the pump control system 520, 600identify the absence of the rescue condition when several successiveglucose and/or predicted glucose measurement values are greater than athreshold value indicative of the rescue carbohydrates having achievedtheir intended effect, thereby resuming insulin delivery by theautomated closed-loop glucose control system in response to a continuingrise of blood sugar to maintain good glycemic control.

In exemplary embodiments, the pump control system 520, 600 also detectsor otherwise identifies an exit condition in response to a mealannouncement or other indication of a meal received from the user.Additionally, in one or more embodiments, the pump control system 520,600 initiates a timer upon entering the rescue mode or otherwiseinitiating the limited delivery (e.g., task 816) and automaticallyterminating the rescue mode when the timer value exceeds a maximumthreshold duration for the rescue recovery period. Thus, the pumpcontrol system 520, 600 ensures the period of limited delivery is onlytemporary before reverting back to the original delivery configurationfor continued regulation of the user's glucose level. In an exemplaryembodiment, the maximum threshold duration is a fixed duration of timethat the safe (or reduced) delivery rate can be delivered withoutadversely affecting the glycemic outcome. That said, in otherembodiments, the maximum threshold duration may be customizable orpatient-specific to reflect varying physiological responses. Forexample, the maximum threshold duration may be chosen to be equal to atypical postprandial period required for the user's glucose level topeak after consuming rescue carbohydrates, thereby allowing the normaldelivery configuration to assist in reducing the user's glucose level ifthe sensor glucose measurements do not exhibit a postprandial dip. Insuch embodiments, a patient-specific maximum threshold duration may bedetermined based on historical measurement data or the like to reflecteach user's individual physiology and varying amount of time forreaching a postprandial peak.

It should be noted that any number of exit conditions may be monitoredfor and/or detected in parallel. For example, the pump control system520, 600 may continually monitor sensor glucose measurement values andcharacteristics thereof for indication that the rescue condition is nolonger present while also implementing a timeout period and monitoringfor any potential meal announcements. By limiting the limited insulindelivery to a temporary duration, rescue carbohydrates may be allowed toachieve their intended effect without risking a potential hyperglycemicevent.

After identifying an exit condition, the pump control system 520, 600automatically restores operation of the infusion device 502 to theinitial operating mode and/or the initial delivery settings prior todetecting the rescue condition. For example, the pump control system520, 600 may restore a maximum delivery rate and/or dosage criteriaassociated with the closed-loop operating mode. Similarly, if othercontrol parameters for the closed-loop operating mode were adjusted(e.g., PID gain coefficients), the pump control system 520, 600 mayrestore those control parameters to their initial values. In otherembodiments, the pump control system 520, 600 restores the originalinsulin delivery by automatically transitioning from a rescue mode (orsafe mode) back to the original closed-loop operating mode or otherautonomous mode preceding the rescue mode. Thus, the pump control system520, 600 may resume operating the motor 507 in a manner configured toreduce the difference between the current sensor glucose measurementfrom the sensing arrangement 504 and a target glucose value as describedabove.

To briefly summarize, the subject matter described herein allows forunannounced rescue carbohydrates consumed by a user to achieve theirintended effect unimpeded by the current operating mode in effect whenthey were consumed by temporarily limiting the delivery of insulin. Inthis manner, potential hypoglycemic events are more readily avoided byconsumption of rescue carbohydrates. At the same time, the period oflimited delivery is itself limited, so as to not interfere withlong-term regulation of the user's glucose level and provide protectionfrom hyperglycemic events. Accordingly, better overall regulation of theuser's glucose level can be achieved without requiring the user toundertake any additional actions upon consuming rescue carbohydrates(i.e., the user does not need to determine the amount of carbohydratesand make a corresponding announcement, manually suspend delivery, or thelike).

For the sake of brevity, conventional techniques related to glucosesensing and/or monitoring, closed-loop glucose control, and otherfunctional aspects of the subject matter may not be described in detailherein. In addition, certain terminology may also be used in the hereinfor the purpose of reference only, and thus is not intended to belimiting. For example, terms such as “first”, “second”, and other suchnumerical terms referring to structures do not imply a sequence or orderunless clearly indicated by the context. The foregoing description mayalso refer to elements or nodes or features being “connected” or“coupled” together. As used herein, unless expressly stated otherwise,“coupled” means that one element/node/feature is directly or indirectlyjoined to (or directly or indirectly communicates with) anotherelement/node/feature, and not necessarily mechanically.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or embodiments described herein are not intended tolimit the scope, applicability, or configuration of the claimed subjectmatter in any way. For example, the subject matter described herein isnot necessarily limited to the infusion devices and related systemsdescribed herein. Moreover, the foregoing detailed description willprovide those skilled in the art with a convenient road map forimplementing the described embodiment or embodiments. It should beunderstood that various changes can be made in the function andarrangement of elements without departing from the scope defined by theclaims, which includes known equivalents and foreseeable equivalents atthe time of filing this patent application. Accordingly, details of theexemplary embodiments or other limitations described above should not beread into the claims absent a clear intention to the contrary.

What is claimed is:
 1. A method of operating an infusion device todeliver fluid to a body of a user, the method comprising: autonomouslyoperating the infusion device to deliver the fluid based at least inpart on measurement values for a physiological condition in the body ofthe user, the physiological condition being influenced by the fluiddelivered by the infusion device; detecting a rescue condition based onthe measurement values; and in response to detecting the rescuecondition, limiting delivery of the fluid while autonomously operatingthe infusion device.
 2. The method of claim 1, wherein detecting therescue condition comprises determining a rate of change associated withthe measurement values is greater than a threshold value.
 3. The methodof claim 1, further comprising verifying at least one of the measurementvalues is less than a monitoring threshold prior to detecting the rescuecondition.
 4. The method of claim 3, wherein detecting the rescuecondition comprises determining a rate of change associated with one ormore recent measurement values of the measurement values is greater thana threshold value.
 5. The method of claim 1, further comprising:detecting an absence of the rescue condition based on one or more of themeasurement values after limiting the delivery of the fluid; and inresponse to detecting the absence of the rescue condition, restoring thedelivery of the fluid.
 6. The method of claim 5, wherein: limiting thedelivery of the fluid comprises adjusting a delivery setting associatedwith the autonomously operating of the infusion device from an initialvalue; and restoring the delivery of the fluid comprises restoring thedelivery setting to the initial value.
 7. The method of claim 1,wherein: autonomously operating the infusion device comprisesautonomously operating the infusion device to deliver a variable rate ofinfusion based at least in part on the measurement values and a targetvalue for the physiological condition; and limiting the delivery of thefluid comprises temporarily capping the variable rate.
 8. The method ofclaim 1, wherein: autonomously operating the infusion device comprisesautonomously operating the infusion device to deliver a variable rate ofinfusion based at least in part on the measurement values and a targetvalue for the physiological condition; and limiting the delivery of thefluid comprises autonomously operating the infusion device to deliver asafe basal rate of infusion.
 9. The method of claim 1, wherein:autonomously operating the infusion device comprises autonomouslyoperating the infusion device in a closed-loop operating mode toregulate the measurement values to a target value for the physiologicalcondition; and limiting the delivery of the fluid comprises autonomouslyoperating the infusion device in a safe mode.
 10. The method of claim 1,wherein: autonomously operating the infusion device comprisesautonomously operating the infusion device to deliver the fluid in aclosed-loop mode based at least in part on the measurement values;limiting the delivery of the fluid comprises autonomously operating theinfusion device to deliver the fluid in a rescue mode; and a firstmaximum rate of infusion associated with the rescue mode is less than asecond maximum rate of infusion associated with the closed-loop mode.11. The method of claim 10, further comprising: detecting an exitcondition while autonomously operating the infusion device to deliverthe fluid in the rescue mode; and in response to detecting the exitcondition, resuming autonomously operating the infusion device todeliver the fluid in the closed-loop mode.
 12. The method of claim 1,further comprising verifying an absence of a meal indication prior tolimiting the delivery of the fluid.
 13. The method of claim 1, furthercomprising after limiting the delivery of the fluid, restoring thedelivery of the fluid in response to a meal indication.
 14. An infusionsystem comprising: a sensing arrangement to obtain measurement valuesfor a physiological condition from a body of a user; and an infusiondevice including an actuation arrangement operable to deliver fluid tothe body of the user and a control system coupled to the actuationarrangement, the fluid influencing the physiological condition of theuser, wherein the control system is coupled to the sensing arrangementto autonomously operate the actuation arrangement to deliver a variablerate of infusion based on the measurement values, detect a rescuecondition based on the measurement values, and temporarily limit thevariable rate of infusion in response to the rescue condition.
 15. Theinfusion system of claim 14, wherein the control system detects therescue condition when a rate of change between successive values of themeasurement values is greater than a first threshold value.
 16. Theinfusion system of claim 14, wherein the control system automaticallyrestores the variable rate of infusion based on one or more of themeasurement values after temporarily limiting the variable rate ofinfusion.
 17. The infusion system of claim 14, wherein the infusiondevice includes a data storage element to maintain a delivery settingassociated with autonomously operating the actuation arrangement,wherein the control system temporarily limits the variable rate ofinfusion by modifying the delivery setting.
 18. An infusion devicecomprising: an actuation arrangement operable to deliver fluid to a bodyof a user; a data storage element to maintain control parameters for aclosed-loop operating mode; a communications interface to receivemeasurement values indicative of a physiological condition in the bodyof the user influenced by the fluid; and a control module coupled to theactuation arrangement, the data storage element, and the communicationsinterface to autonomously operate the actuation arrangement to deliver avariable rate of infusion based on the measurement values and thecontrol parameters in accordance with the closed-loop operating mode,detect a rescue condition based on one or more of the measurementvalues, and temporarily limit the variable rate of infusion in responseto the rescue condition.
 19. The infusion device of claim 18, whereinthe control module temporarily limits the variable rate by autonomouslyoperating the actuation arrangement in accordance with a safe mode. 20.The infusion device of claim 18, wherein the control module detects therescue condition when a rate of change associated with a firstmeasurement value of the one or more measurement values is greater thana rescue detection threshold after a preceding measurement value of theone or more measurement values is less than a rescue monitoringthreshold.